Method and Apparatus for Pressure Infusion and Temperature Control of Infused Liquids

ABSTRACT

A method and apparatus for pressure infusion and temperature control of infused liquids includes a receptacle for receiving a liquid-filled bag containing intravenous solution or other liquid and an inflatable pressure device. The inflatable pressure device is disposed within a pressure device bag and is positioned proximate the liquid-filled bag in the receptacle. The inflatable pressure device expands within the pressure device bag upon inflation and exerts pressure on the liquid-filled bag. A heating element may be disposed on the inflatable pressure device bag to heat the liquid-filled bag to a desired temperature. The liquid may alternatively be maintained at a desired temperature, while flowing to a patient via a heating assembly disposed along a tube. The heating assembly includes a sleeve having a slot for receiving the tube and a plurality of individually controlled heaters. An infrared sensing device is mounted proximate a drip chamber to ascertain a drip count, while a temperature sensor is disposed within a holder that is positioned toward the entry site on a patient. A heat controller controls the heaters based on a drip count, while a safety controller disables heater operation in response to liquid temperature exceeding the desired temperature. Thus, the safety controller and heat controller, in combination, control the heating assembly heaters based on liquid temperature and flow rate, respectively. Alternatively, the liquid-filled bag may be heated to a desired temperature whereby the heating assembly includes a single heater controlled by a controller to maintain the liquid at the desired temperature during infusion of the liquid into a patient.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/040,885, filed Mar. 3, 1997, entitled “Methodand Apparatus for Measurement and Control of Temperature for InfusedLiquids”, and U.S. Provisional Patent Application Ser. No. 60/062,315,filed Oct. 17, 1997, entitled “Method and Apparatus for PressureInfusion and Temperature Control of Infused Liquids”. The disclosures ofthe foregoing provisional patent applications are incorporated herein byreference in their entireties.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention pertains to pressurized infusion and temperaturecontrol apparatus or systems for infused liquids. In particular, thepresent invention is directed toward pressurized infusion of liquidsinto a patient and/or temperature control of that liquid during infusioninto a patient.

2. Discussion of Prior Art

Generally, intravenous (I.V.) solution or other liquids are infused intoa patient by disposing a liquid-filled bag containing intravenoussolution or other liquid on a pole structure to permit gravitationalforces to direct liquid from the liquid-filled bag through anintravenous or other tube into the patient. However, gravitationalforces may be insufficient to drive certain viscous liquids, such asrefrigerated blood, into the patient, or drive liquids into the patientat a sufficient rate. The prior art has attempted to overcome theaforementioned inadequacies of gravitational forces by applying pressureto the liquid-filled bag to enhance liquid flow from the liquid-filledbag to the patient. For example, U.S. Pat. No. 4,090,514 (Hinck et al)discloses a pressure infusion device including a bladder wherein thedevice encases a liquid-filled bag with the bladder surrounding at leasteighty percent of that bag. Upon inflation of the bladder, liquid withinthe liquid-filled bag is infused under pressure to a patient. Further,U.S. Pat. No. 4,551,136 (Mandl) discloses a pressure infuser includingan inflatable bladder that wraps about a liquid-filled bag. The bladderincludes a vertical strip at each end and a strap that wraps about thebladder and liquid-filled bag. The vertical strips overlap to provide acomplete wrap about the liquid-filled bag, while the strap maintains theoverlapping strip portions in contact. The bladder is inflated to adesired pressure whereby pressure is applied by the bladder to theliquid-filled bag to infuse liquid into a patient.

The Hinck et al and Mandl devices suffer from several disadvantages. Inparticular, the Hinck et al device includes a bladder that substantiallysurrounds a liquid-filled bag, however, the bladder may not expandsufficiently to apply adequate pressure to the liquid-filled bag whensmall volumes of liquid are present within the liquid-filled bag,thereby operating less efficiently when smaller volumes of liquid residewithin the liquid-filled bag and requiring premature replacement of theliquid-filled bag prior to utilization of liquid within that bag.Similarly, the Mandl infuser utilizes a strap to maintain a bladderabout a liquid-filled bag wherein pressure exerted by the bladder on theliquid-filled bag is focused substantially coincident the strap, therebyoperating less efficiently, especially when smaller volumes of liquidreside within the liquid-filled bag, since various pressures are appliedto different portions of the liquid-filled bag (e.g., the bladderportions disposed near the strap apply the greatest amounts of pressure,while the bladder portions disposed furthest from the strap apply theleast amounts of pressure), and requiring premature replacement of theliquid-filled bag prior to utilization of liquid within that bag. Inother words, when the liquid-filled bags become partially depleted andthin, the bladders of the Hinck et al and Mandl devices may not maintainadequate pressure on the thinner bags for infusion of liquid into apatient. Further, the bladders of these devices generally includecertain dimensions, thereby only being compatible or satisfactorilyoperable with liquid-filled bags of a particular size. Moreover, theHinck et al and Mandl devices do not thermally treat the liquid-filledbags in any manner during infusion.

In addition to providing pressurized infusion as described above, it isdesirable during surgical procedures to maintain a patient's bodytemperature at approximately 98.6° F. or 37° C. (i.e., normal bodytemperature) to avoid hypothermia and complications that may arise withminute decreases in body temperature (e.g., decreases of approximately2-3° C.). Further, infusion into a patient of liquids havingtemperatures below the normal body temperature may produce furthercomplications, such as shock, cardiac dysfunction, increased coagulationtime, and in certain patients, clumping of blood cells.

In order to avoid hypothermia and other complications described above,warmers are typically employed during surgical or other medicalprocedures to maintain the temperature of infused liquids at or nearbody temperature. Generally, prior art warmer systems employ varioustechniques to heat infused liquids. In particular, infused liquid may bedirected within tubing or a bag through a solution bath (e.g., warmedliquid); infused liquid may be directed about a tube through whichwarmer liquid flows in an opposing direction; infused liquid maytraverse tubing or be stored in a bag placed proximate heating plates;infused liquid may be disposed in a bag placed about a heating element;infused liquid may be warmed by a heat exchanger in the form of acassette placed between heating plates; or infused liquid may be warmedvia heated air or microwave energy. For example, U.S. Pat. No. 1,390,500(Christian) discloses a flexible water heater and dripper wherein waterand other liquid flow from a container and are heated while traversing aflexible heating element having a conduit. The heating element includesresistance coils and is connected to a rheostat having a sliding memberto control current to the heating device to provide a desired degree ofheat.

U.S. Pat. No. 1,726,212 (Bucky) discloses an irrigator including acontainer filled with liquid having a heater for heating the liquid to adesired temperature. A bulb pumps air into the container to produce apressure that drives the liquid through tubing to an irrigation site.

U.S. Pat. No. 1,995,302 (Goldstein) discloses an adjustable heatinginfusion apparatus wherein a flexible tube conveying fluid is heated viaan electric resistance wire spirally wound about the tube outer surface.The wire spirals are more concentrated at a tube proximal end to raiseliquid temperature toward a desired level, while the remaining windingsmaintain the liquid temperature at substantially that desired level. Athermostatic current control regulates current to the resistance wire tomaintain a predetermined temperature.

U.S. Pat. No. 3,247,851 (Seibert) discloses an apparatus for applyingliquids to the body wherein a heating unit extends along a length of atube to heat liquid as the liquid flows from a receptacle. The heatingunit includes heating wires and a thermostat to heat the liquid in thetube.

U.S. Pat. No. 5,250,032 (Carter, Jr. et al) discloses a heater for invivo blood infusion including a housing having a channel for receiving aportion of an intravenous tube. A heating element is mounted proximate aslot disposed within the channel to heat the tube wherein the heatingelement is controlled by a control circuit and powered by batteries. Thecontrol circuit controls the heating element in response to sensedtemperatures.

U.S. Pat. No. 5,254,094 (Starkey et al) discloses a physiological fluidwarmer including two chambers having coils for fluid to flow, while awarming liquid flows through the chambers along the coils in a directionopposite to the fluid flow. The fluid warmer may be controlled by amicroprocessor to operate in response to either fluid or warming liquidtemperature.

The prior art warmer systems described above suffer from severaldisadvantages. In particular, the prior art warmer systems heatingliquid within an intravenous or other tube tend to employ and control asingle heating element disposed along the tube, thereby limiting controlaccuracy of the liquid temperature and typically producing hot spots(e.g., certain sections of the tube may become warmer than othersections of the tube) along the tube. Some of the prior art warmersystems require pre-heating of a liquid-filled bag prior to use in andexternal of those systems, thereby requiring additional time to heat theliquid. Further, the prior art warmer systems heating liquid within anintravenous or other tube typically rely on gravitational forces todirect the liquid to the patient. These gravitational forces may beinadequate to produce desired flow rates or enable flow of viscoussolutions as described above. Moreover, certain prior art warmer systemsheat liquid flowing within an intravenous or other tube at a sitelocated a substantial distance from the patient entry point, therebypermitting heated liquid to cool by the time the heated liquid reachesthe patient. In addition, the prior art warmer systems typically controlliquid heating based solely on temperature measurements of the liquid,thereby limiting control options and providing for less accuratecontrol. The prior art warmer systems typically maintain activation ofheating elements in cases of excessive liquid or heating elementtemperatures or interruptions in liquid flow, thereby enabling theheating elements to heat the liquid to temperatures beyond the liquidutilization temperature range and possibly injure a patient and/ordamage an intravenous or other tube. A further disadvantage of the priorart warmer systems heating liquid within an intravenous or other tube isthat the temperature of liquid contained within a liquid-filled bag orreceptacle is typically substantially below a desired temperature,thereby requiring significant heating of the liquid during infusion asthe liquid traverses the tube.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to infuse liquidunder pressure into a patient by exerting pressure in a downward fashionon a liquid-filled bag until virtually all of the liquid is spent.

It is another object of the present invention to infuse heated liquidunder pressure into a patient.

Yet another object of the present invention is to control temperature ofinfused liquid via multiple individually controlled heaters disposedalong an intravenous or other tube.

Still another object of the present invention is to control temperatureof infused liquid flowing in an intravenous or other tube based ontemperature and flow rate of the infused liquid.

A further object of the present invention is to control temperature ofinfused liquid by heating a liquid-filled bag or receptacle to a desiredtemperature and maintaining liquid from the liquid-filled bag at thattemperature during infusion into a patient via a heater disposed alongan intravenous or other tube.

The aforesaid objects are achieved individually and in combination, andit is not intended that the present invention be construed as requiringtwo or more of the objects to be combined unless expressly required bythe claims attached hereto.

According to the present invention, a method and apparatus for pressureinfusion and temperature control of infused liquids includes areceptacle for receiving a liquid-filled bag containing intravenoussolution or other liquid and an inflatable pressure device or bellows.The bellows is disposed within a bellows bag and is positioned proximatethe liquid-filled bag in the receptacle. The receptacle is typicallysuspended from an intravenous pole or other structure. A conventionalbulb is manipulated to inflate the bellows wherein the bellows expandswithin the bellows bag upon inflation and exerts pressure on theliquid-filled bag to direct liquid from the liquid-filled bag through anintravenous or other tube to a patient. Further, the bellows bagincludes a pocket that may receive a heating element and conductiveplate to enable pressurized infusion of heated liquid into a patient.The heating element heats the liquid-filled bag to a desired temperaturethrough the conductive plate, while the bellows exerts pressure on theliquid-filled bag to direct heated liquid from the liquid-filled bag tothe patient in substantially the same manner described above.

Intravenous solution or other liquid may be maintained at a desiredtemperature during infusion via a heating assembly disposed along anintravenous or other tube. The tube extends to a patient entry site froma drip chamber that is coupled to a liquid-filled bag containingintravenous solution or other liquid. The liquid-filled bag is typicallysuspended from an intravenous pole or other structure. The heatingassembly includes a sleeve having a substantially centrally disposedslot for receiving a portion of the tube and a plurality of individuallycontrolled heaters located proximate the slot. The tube portion istypically inserted into the slot via a special tool, while the sleeve isdisposed within a jacket. An infrared sensing device is mountedproximate the drip chamber to ascertain a drip count rate or, in otherwords, a liquid flow rate wherein a heat controller controls the heatersbased on the drip count rate. In addition, a temperature sensor isdisposed within a thermocouple holder that is positioned toward theentry site on the patient. The thermocouple holder positions thetemperature sensor proximate the tube to obtain an accurate temperaturemeasurement of the liquid near the entry site. A temperature signal issent from the temperature sensor to an additional safety controller thatdisplays the liquid temperature and disables the heaters in response tothe liquid temperature being equal to or exceeding the desiredtemperature. Thus, the safety controller and heat controller, incombination, control the heating assembly heaters to maintain the liquidtemperature substantially at the desired temperature based on liquidtemperature and flow rate, respectively, wherein disablement of theheating assembly heaters by the safety controller overrides any heatercontrols given by the heat controller. Alternatively, the liquid-filledbag may be heated to a desired temperature and the heating assemblysleeve may contain a single heater controlled by a controller tomaintain the liquid at the desired temperature during infusion of theliquid into a patient.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of specific embodiments thereof,particularly when taken in conjunction with the accompanying drawingswherein like reference numerals in the various figures are utilized todesignate like components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in perspective of a pressurized infusion systemaccording to the present invention.

FIG. 2 is a side view in elevation of the pressurized infusion system ofFIG. 1.

FIG. 3 is a front view in elevation of a receptacle of the pressurizedinfusion system of FIG. 1 for containing a liquid-filled bag and abellows disposed within a bellows bag.

FIG. 4 is a side view in elevation of a bellows of the pressurizedinfusion system of FIG. 1.

FIG. 5 is a side view in elevation of a bellows bag for containing thebellows of FIG. 4.

FIG. 6 is a view in perspective of a pressurized infusion system thatheats infused liquids according to another embodiment of the presentinvention.

FIG. 7 is a side view in elevation of the pressurized infusion system ofFIG. 6.

FIG. 8 is a view in elevation of a conductive plate of the pressurizedinfusion system of FIG. 6.

FIG. 9 is a view in elevation of a heating element of the pressurizedinfusion system of FIG. 6 for heating infused liquids.

FIG. 10 is an electrical schematic diagram of an exemplary heatercontrol circuit for the pressurized infusion system of FIG. 6.

FIG. 11 is a view in perspective of a temperature control system forinfused liquids according to yet another embodiment of the presentinvention.

FIG. 12 is a front view in elevation of a control panel box of thetemperature control system of FIG. 11.

FIG. 13 is an exploded view in perspective of a heating assembly of thetemperature control system of FIG. 11 receiving a portion of anintravenous or other tube.

FIG. 14 is an exploded view in perspective of a portion of anintravenous or other tube inserted within the heating assembly of FIG.13 via a tool.

FIG. 15 is a view in perspective of the heating assembly of FIG. 13encased within a jacket.

FIG. 16 is a view in elevation of the tool of FIG. 14 for inserting aportion of an intravenous or other tube within the heating assembly ofFIG. 13.

FIG. 17 is a view in elevation of a portion of a drip detector of thetemperature control system of FIG. 11 having an infrared emitter todetect drips of infused liquid.

FIG. 18 is a view in elevation of a portion of a drip detector of thetemperature control system of FIG. 11 having infrared detectors todetect drips of infused liquid.

FIG. 19 is a view in elevation of a thermocouple holder of thetemperature control system of FIG. 11 for maintaining a temperaturesensor in the proper position to provide an accurate temperaturemeasurement of liquid within an intravenous or other tube.

FIG. 20 is an electrical schematic diagram of an exemplary controlcircuit of the temperature control system of FIG. 11 for controllingsystem operation.

FIG. 21 is an electrical schematic diagram of an exemplary circuit boardof the control circuit of FIG. 20.

FIG. 22 is a procedural flow chart illustrating the manner in whichtemperature control system heaters are disabled in response to a liquidtemperature measurement being equal to or in excess of a desired liquidtemperature within the temperature control system of FIG. 11.

FIG. 23 is a procedural flowchart illustrating the manner in whichtemperature control system heaters are controlled based on flow ratewithin the temperature control system of FIG. 11.

FIG. 24 is a view in perspective of a temperature control system forinfused liquids heating both a liquid-filled bag and liquid within anintravenous or other tube according to still another embodiment of thepresent invention.

FIG. 25 is an electrical schematic diagram of an exemplary controlcircuit for the temperature control system of FIG. 24.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A pressurized infusion apparatus or system for irrigating a patient ordirecting infused liquids into a patient is illustrated in FIGS. 1-2.Specifically, system 2 a is typically mounted on a conventionalintravenous (I.V.) pole 4 and includes a receptacle 6 for containingintravenous solution or other liquid and engaging pole 4, a pressuregauge 8, an inflatable pressure device or bellows 10, a bulb 12 forregulating fluid pressure within the bellows via a hose 21, and anintravenous or other tube 72 for directing liquid from the receptacle toa patient. Receptacle 6 typically receives a liquid-filled bag 14 (e.g.,a bag containing intravenous solution or other liquid) and bellows 10wherein the bellows is disposed within a bellows bag 32 (FIG. 5) andpositioned adjacent the liquid-filled bag. Hose 21 extends betweenbellows 10 and bulb 12 wherein manipulation of the bulb drives fluidinto or from the bellows through hose 21. Hose 21 is typicallyimplemented by a conventional or other type of hose, may be of any sizeor shape and may be constructed of any suitable materials. Inflation ofbellows 10 via bulb 12 enables the bellows to expand within bellows bag32 and apply pressure to liquid-filled bag 14, thereby driving liquidfrom the liquid-filled bag through tube 72 to a patient. Bulb 12includes a valve 9 to release fluid from bellows 10 such that the bulbmay add or reduce pressure applied by the bellows to liquid-filled bag14 based on pressure levels within the bellows indicated by pressuregauge 8. For example, increased fluid pressure within the bellowsincreases pressure exerted by the bellows onto the liquid-filled bag,while decreased fluid pressure within the bellows reduces pressureexerted by the bellows onto the liquid-filled bag. Pressure gauge 8 maybe implemented by any conventional or other type of pressure gauge ordevice, and provides a measurement and indication of fluid pressurewithin the bellows produced by manipulation of bulb 12. The bellows andbellows bag each include a substantially triangular or wedge shape andare typically disposed in receptacle 6 with their respective portionshaving the greatest thickness positioned toward the upper portion ofliquid-filled bag 14. However, the bellows and bellows bag may be of anyshape or size, while the bellows may be implemented by any devicecapable of applying pressure to the liquid-filled bag. Pressure isapplied by bellows 10 to liquid-filled bag 14 in a downward manner todrive the liquid downward, to control the flow rate of the liquid and toproduce an even flow. It is to be understood that the terms “upper”,“lower”, “up”, “down”, “front”, “back”, “rear”, “top”, “bottom”, “side”,“left”, “right”, “far”, “near”, “height”, “width”, “thickness” and“length” are used herein merely to describe points of reference and donot limit the present invention to any particular configuration ororientation.

Referring to FIG. 3, receptacle 6 includes a compartment or storage area23 and a generally triangular projection 16 extending from the upperportion of the compartment to engage pole 4 (FIGS. 1-2). The compartmentis in the form of a substantially rectangular bag having an open topportion and includes dimensions greater than the combined dimensions ofliquid-filled bag 14 and bellows bag 32 (i.e., containing bellows 10) inorder to receive these items. The front portion of compartment 23includes strips 18, 20 that are fastened together via a zipper 22 or anyother fastening device. Zipper 22 is typically implemented by aconventional zipper and generally extends along a substantially centrallongitudinal axis of the compartment front portion to fasten an edge ofstrip 18 to an adjacent or facing edge of strip 20. The zipper enablesthe compartment front portion to be substantially closed to maintainbellows bag 32 (i.e., containing bellows 10) and liquid-filled bag 14within the compartment. In other words, zipper 22 essentially enablesplacement and removal of the bellows bag (i.e., containing the bellows)and liquid-filled bag within the compartment. The zipper or otherfastening device may be disposed anywhere on the compartment in anyfashion to facilitate placement and removal of items within thecompartment. The compartment rear portion typically includes an opening(not shown) to permit fluid transfer between bulb 12 and bellows 10 viahose 21 (FIG. 2). The opening may be of any size or shape capable ofpermitting the hose to extend to the bellows.

Generally triangular projection 16 extends from the upper back portionof compartment 23 and includes openings 24, 26 and a loop 28. Openings24, 26 are defined toward the projection center with opening 24 disposedbetween openings 26. These openings enable pressure gauge 8 (FIGS. 1-2)to be mounted on the receptacle. Loop 28 is disposed toward the upperportion of a rear exterior surface of the projection to engage pole 4and to enable receptacle 6 to be attached to the pole. The receptaclehouses the liquid-filled bag and bellows bag (i.e. containing thebellows) to produce pressurized infusion of liquids as described above.The compartment, projection and loop may be of any size or shape, andmay be constructed of plastic, rubber or any other suitable materials.By way of example only, the compartment has a height of approximatelyten inches and a width of approximately nine inches, while theprojection extends approximately three inches from the compartment withthe loop extending approximately one inch from the projection.

Bellows 10 for driving liquid from liquid-filled bag 14 to a patient isillustrated in FIG. 4. Specifically, bellows 10 is generally righttriangular and in the form of a wedge. The bellows may be of any size orshape, may be constructed of plastic, rubber, fabric or any othersuitable materials, and may be implemented by any conventional or othertype of expandable device. By way of example only, the bellows has aheight of approximately nine inches, a width of approximately four andone-half inches and an uninflated thickness of approximately four inches(i.e., the thickness varies depending on the amount of inflation). Theupper portion and sides of the bellows typically include a series ofpeaks and recesses in a sawtooth configuration extending between frontand rear surfaces of the bellows similar in structure to an accordion.An inlet or port 30 is disposed on a rear exterior surface of thebellows to permit fluid to flow into and from the bellows. The port istypically connected to bulb 12 via hose 21 (FIGS. 1-2), and may be ofany size or shape and disposed anywhere on the bellows. When bulb 12 ismanipulated to drive fluid into bellows 10, the bellows expandslaterally and downward within bellows bag 32 (FIG. 5) and appliespressure to liquid-filled bag 14 to drive liquid to a patient asdescribed above.

Bellows 10 is disposed within bellows bag 32 and is positioned inreceptacle 6 adjacent liquid-filled bag 14 as described above whereinbellows bag 32 for housing the bellows is illustrated in FIG. 5.Specifically, bellows bag 32 is generally right triangular in the formof a wedge with a front tilted surface and includes dimensions greaterthan the dimensions of bellows 10 to accommodate the bellows in anexpanded or compressed state. The bellows bag is typically constructedof cordura nylon, however, the bellows bag may be constructed of anyfabric or suitable materials. Bellows bag 32 includes an opening 33disposed at the bellows bottom for insertion of the bellows into thebellows bag. A flap 34 is disposed proximate opening 33 and extends fromthe bottom portion of the bellows bag to cover opening 33 and tomaintain the bellows within the bellows bag. Further, a port opening(not shown) may be defined in the bellows bag rear surface to enablefluid transfer between bellows 10 and bulb 12 (FIG. 2) via port 30 (FIG.4) and hose 21 as described above. In addition, a pocket 35 may bedisposed on the bellows bag front tilted surface for receiving aconductive plate and heating element to heat liquid-filled bag 14 (FIG.6) as described below. The bellows bag may be of any size or shape and,by way of example only, includes a height of slightly greater thanapproximately nine inches, a width of slightly greater thanapproximately four and one-half inches and a depth of approximatelythree inches.

Operation of the pressurized infusion system is described with referenceto FIGS. 1-5. Specifically, bellows 10 is disposed within bellows bag 32and is placed along with liquid-filled bag 14 in receptacle 6. Thereceptacle is typically mounted on pole 4 via loop 28 as describedabove. Bellows bag 32 (i.e., containing bellows 10) is disposedproximate liquid-filled bag 14 such that liquid-filled bag 14 compressesthe bellows within bellows bag 32. Bulb 12 is manipulated to directfluid into bellows 10 through hose 21 to enable the bellows to expandwithin bellows bag 32 and exert pressure in a downward manner onliquid-filled bag 14 to drive liquid to a patient. Valve 9 may bemanipulated to release pressure from the bellows as described above suchthat the pressure and flow rate of the liquid may be controlled.Pressure gauge 8 measures and displays the fluid pressure within bellows10 produced by manipulation of the bulb, and upon reaching the desiredpressure, liquid is driven from liquid-filled bag 14 to a patient at acertain flow rate.

Alternatively, system 2 a may further include a heater or heatingelement to heat liquid-filled bag 14 for pressurized infusion of heatedliquid into a patient as illustrated in FIGS. 6-7. Specifically, system2 b is substantially similar to system 2 a described above except thatsystem 2 b heats liquid-filled bag 14 or maintains the temperature of apre-heated liquid-filled bag for infusion of heated liquid into thepatient. Bellows 10 is disposed within bellows bag 32 and is placedalong with liquid-filled bag 14 in receptacle 6 as described above.Bellows bag 32 (i.e., containing bellows 10) is disposed adjacentliquid-filled bag 14 such that the bellows expands within the bellowsbag via inflation by bulb 12 to exert pressure on liquid-filled bag 14and drive liquid to a patient in substantially the same manner describedabove. A heater or heating element 36 and conductive plate 38 aredisposed within pocket 35 of bellows bag 32 (FIG. 5) such that theheating element and conductive plate are located adjacent liquid-filledbag 14. Pocket 35 is typically formed on bellows bag 32 via additionalmaterial extending for a substantial portion of the bellows bag heightand having a substantially central opening for permitting the conductiveplate to apply heat from the heating element to liquid-filled bag 14. Asbellows 10 is inflated, the bellows presses conductive plate 38 againstliquid-filled bag 14 to heat the liquid contained within that bag. Asubstantially rectangular control box 40 is mounted on pole 4 andincludes circuitry to control power supplied to heating element 36.Control box 40 typically receives power from a common wall outlet jackvia power cord 42, and may be of any shape or size and may beconstructed of any suitable materials.

Referring to FIG. 8, conductive plate 38 is generally rectangular havinga notch disposed at the approximate center of its bottom edge. The platetapers slightly along its shorter dimension towards the upper portion ofthe plate and includes truncated or cut-off upper portion corners. Byway of example only, the plate is constructed of copper and has a heightof approximately eight and one-half inches and a width of approximatelyfour and one-half inches, however, the plate may be constructed of anysuitable conductor materials and may be of any size or shape. Theconductive plate applies heat from heating element 36 (FIG. 7) to asubstantial portion of liquid-filled bag 14.

Heating element 36 for applying heat to the liquid-filled bag throughconductive plate 38 is illustrated in FIG. 9. In particular, the heatingelement is substantially rectangular and includes a notch disposed atthe approximate center of its bottom edge. The heating element isdisposed between the conductive plate and bellows bag to convey heatthrough the conductive plate to a substantial portion of theliquid-filled bag. By way of example only, heating element 36 isconstructed of copper and includes a height of approximately four andone-quarter inches and a width of approximately two and one-half inches,however, the heating element may be constructed of any suitableconductor materials and may be of any size or shape.

A control circuit for controlling heating element 36 is illustrated inFIG. 10. Specifically, lines 44, 46 and 48 represent the power receivedfrom power cord 42 (FIG. 7) with line 48 connected to ground. Line 44 isconnected in series with a fuse 50 to protect the circuit from powersurges and spikes. Lines 44, 46 are connected to a power switch 52 thatcontrols power to the circuit. The power switch enables a power supply54 to provide power, typically up to a maximum of 24V, to heatingelement 36 via a controller 56. Controller 56 is connected to powersupply 54 and heating element 36 to control power to the heating elementbased on a temperature measurement. Controller 56, in essence, includesboth control circuitry and a sensor to control heating element 36 basedon a predetermined temperature. The controller measures resistancethrough heating element 36, thereby providing a temperature indication.A predetermined resistance is programmed into controller 56 to provide apreset temperature wherein the controller compares the measured heatingelement resistance to the predetermined resistance to control theheating element. If the measured resistance is below the predeterminedresistance (i.e., measured temperature is below the preset temperature),then controller 56 increases power to the heating element to increaseheat and resistance. Conversely, if the measured resistance is above thepredetermined resistance (i.e., measured temperature is above the presettemperature), controller 56 decreases power to the heating element todecrease heat and resistance. Thus, the controller maintains heatingelement 36 substantially at the predetermined resistance (i.e.,temperature) by passing appropriate amounts of power to the heatingelement. The lines, power supply, heating element and controller may beimplemented by any conventional components, however, by way of exampleonly, controller 56 is implemented by a Minco CT-198 controller. Thecontrol circuitry is typically disposed within controller box 40 (FIG.7) mounted on pole 4 described above.

Operation of the heating and pressurized infusion system is describedwith reference to FIGS. 6-10. Specifically, a temperature or resistanceis preset into controller 56 as described above, while bellows 10 isdisposed within bellows bag 32 and is placed along with liquid-filledbag 14 in receptacle 6. The receptacle is typically mounted on pole 4 asdescribed above. Bulb 12 is manipulated to drive fluid into bellows 10as described above wherein the bellows expands within the bellows bagand presses conductive plate 38, heated via heating element 36, againstthe liquid-filled bag, thereby heating the liquid-filled bag,controlling flow rate and driving liquid to a patient. The controlcircuit measures the resistance of heating element 36 and varies powerto the heating element to maintain temperature of the heating element,and hence, the liquid-filled bag at the predetermined temperature.Alternatively, a pre-heated liquid-filled bag (e.g., heated to 100° F.)may be inserted within receptacle 6 adjacent bellows bag 32 (i.e.,containing bellows 10). Heating element 36 may be controlled viacontroller 56 to maintain the pre-heated liquid-filled bag at thepredetermined temperature, while the bulb and bellows may be used tocontrol flow rate and drive liquid from the pre-heated liquid-filled bagto a patient in substantially the same manner described above.

A temperature control or warming system for heating liquid traversing anintravenous or other tube during irrigation or infusion is illustratedin FIG. 11. The temperature control system may be utilized incombination with the pressure infusion systems described above. Anexemplary configuration includes receptacle 6, a drip chamber 58, a dripdetector 60, an intravenous or other tube 72, a roller lock 62, aheating assembly 64, a connector 66 and a thermocouple holder 68.Receptacle 6 typically contains a liquid-filled bag 14, while beingmounted on an intravenous (I.V.) pole 4. The receptacle may furtherinclude bellows 10 and bellows bag 32 (FIG. 5) with or without heatingelement 36 and conductive plate 38 as described above (FIGS. 2 and 7).Liquid flows from liquid-filled bag 14 to drip chamber 58 having dripdetector 60 surrounding the drip chamber to detect each drip. Dripdetector 60 typically employs an infrared emitter and several infrareddetectors as described below to ensure accurate detection of drips. Tube72 extends from drip chamber 58 wherein roller lock 62 is disposed ontube 72 subsequent the drip chamber to control fluid flow in the tube.After the roller lock, tube 72 traverses heating assembly 64, in theform of a sleeve having heaters disposed therein, to maintain the liquidat a predetermined temperature. Subsequent heating assembly 64, tube 72traverses connector 66 (e.g., a Luer connector) and interfacesthermocouple holder 68. Thermocouple holder 68 maintains a temperaturesensor, preferably an infrared sensor, in the proper position adjacenttube 72 to obtain an accurate temperature measurement of the liquid nearan entry point on a patient. The thermocouple holder is typicallyattached to a patient's limb or body near the entry point via anapproved medical biocompatible adhesive or any other techniques (e.g.,tape). Following thermocouple holder 68, tube 72 extends to the entrypoint to infuse liquid into the patient via a needle or other medicaldevice. A substantially rectangular control panel box 70 is mounted onpole 4 and controls system operation, while displaying the temperatureand drip count to a user. The control panel box may be of any shape orsize and may be constructed of any suitable materials.

Control panel box 70 displays various items and controls systemoperation as illustrated in FIG. 12. Specifically, control panel box 70includes temperature display 74, set point (i.e., predetermined ordesired temperature) display 76, controller program buttons 78, powerswitch 80, counter display 82 and heater indicator lights 84. Powerswitch 80 enables power to the system and is disposed at the approximatecenter of the lower portion of the control panel box front surface.Heater indicator lights 84 are substantially vertically aligned toward afar edge (e.g., rightmost edge as viewed in FIG. 12) of the controlpanel box front surface and are illuminated to indicate activation ofthe heaters, which heaters are activated, and the length of time aheater is activated in a cycle according to the drip rate. Temperatureand set point displays 74, 76 are disposed toward the central portion ofan edge (e.g., leftmost edge as viewed in FIG. 12) of the control panelbox front surface opposing heater indicator lights 84 with temperaturedisplay 74 disposed above set point display 76. Temperature display 74displays the liquid temperature as detected by a temperature sensordescribed below, while set point display 76 displays the predeterminedor desired liquid temperature. Controller program buttons 78 aredisposed below set point display 76 and enable the set point and otherinformation to be programmed into a safety controller described below.The buttons typically include functions, such as up, down, scroll andpage, to program and enter data into the controller. Counter display 82is disposed above power switch 80 between temperature display 74 andindicator lights 84, and displays a count of the drips detected by dripdetector 60 (FIG. 11) during a predetermined time interval. The counterdisplay further indicates proper operation of drip detector 60 and maybe utilized for system diagnostics. Additional displays may be includedon the control panel box front surface to display total drip counts andtotal volume of liquid dispensed. The displays may be implemented by anyconventional LED or LCD or other displays, while the lights and powerswitch may be implemented by any conventional components, such as diodesand switches, respectively. The control panel displays, lights andswitches may be arranged in any fashion and disposed anywhere on thecontrol panel box or on a separate panel.

Referring to FIGS. 13-15, heating assembly 64 typically includes anelongated sleeve 92 having a plurality of heaters 124 disposed thereinto heat liquid in tube 72. Any quantity of sleeves or heating assembliesmay be utilized by the system. Sleeve 92 includes a slot 94 extendinglongitudinally along an upper sleeve surface for receiving a portion oftube 72, and has a generally elliptical cross-section with channels 96,98 defined through the sleeve for accommodating wiring. Typically,channels 96, 98 accommodate voltage wires extending from the heaters toprevent the heaters from heating or burning the wires. The plurality ofheaters are disposed coincident the slot between channels 96, 98 suchthat the tube portion is disposed against the heaters to enabletemperature control of liquid within the tube. Sleeve 92 is designed tosecure the tube portion against the heaters and to provide insulation toprotect the patient from burns. The heaters are typically manufacturedby Watlow, but may be implemented by any conventional or other type ofheater, for example, Kapton heaters. The tube portion is typicallyinserted within slot 94 via a tool 88 described below. A temperaturesensor 86 is initially positioned external of heating assembly 64 withwires extending from the sensor to the control panel box. Channel 96(e.g., the leftmost channel in FIGS. 13-15) typically accommodates wiresextending between control panel box 70 and the heaters, while channel 98(e.g., the rightmost channel in FIGS. 13-15) typically accommodateswires for temperature sensor 86. The tube portion is typically disposedin the heating assembly with temperature sensor 86 subsequently disposedwithin thermocouple holder 68 (FIG. 11) as described below. A jacket 90,typically constructed of canvas, encases heating assembly 64 and isclosed via a zipper 100 that extends along substantially the entirelength of sleeve 92 to protect users, patients and equipment from burnsand to secure the heating sections of the assembly. Jacket 90 istypically placed over the heating assembly after placement of the tubeportion and temperature sensor as described above. The sleeve may beconstructed of plastic, silicon, rubber or any suitable materials andmay be of any size or shape to accommodate various heaters and any sizedtube portion from any type of tube.

Typically, heating assembly 64 includes three twenty watt, 120V heaters124 individually controlled by a heat controller described below.However, any quantity or combination of heaters having various powercharacteristics may be utilized. For example, three forty watt heaters,or a forty watt and a twenty watt heater may be utilized in the heatingassembly. Heaters 124 are each controlled, in part, by a heat controlleror processor based on a count of drips detected, during a predeterminedtime interval, within drip chamber 58 (FIG. 11) via an infrared emitterand infrared detectors described below. In other words, the processoractivates individual heaters based on liquid flow rate or the dripcount. Heaters 124 each directly supply heat to tube 72 via heatingassembly 64 as described above, and may be activated by the processor inany combination (e.g., a first heater may be activated, while a secondheater is activated intermittently, all heaters may be activated or onlya single heater may be activated) as described below. The processorcontrols each heater 124 based on a drip count by controlling linevoltage to a solid state switching relay associated with that heater toactivate that heater for a specified time interval and then deactivatethe heater (i.e., the drip count determines which heaters to activateand the time interval for activation).

The utilization of multiple heaters 124 provides enhanced control, ascompared to utilization of a single heater, for various flow rangeswithout burning tube 72. Further, the multiple heater arrangement avoidshot spots by selectively heating different portions of the tube. Thetemperature control system further includes a separate safety controllerthat disables heaters 124 in response to detecting temperatures equal toor above the predetermined or desired temperature. This avoids residualheat (e.g., heat applied to the tube after a malfunction or aninterruption in the liquid flow) and prevents temperature change fromreaching a patient. The disablement of heaters 124 by the safetycontroller overrides any heater controls issued by the heat controller.Thus, operation of heaters 124 is controlled by criteria empiricallyobtained based on measured drip count and temperature.

The system further includes various safety features to disable heaters124 based on detection of certain events. For example, when the dripcounter malfunctions, the temperature sensor becomes loose at the userend, the liquid-filled bag is tipped or relatively empty, the liquidtemperature is equal to or exceeds a threshold temperature range (e.g.,approximately 104-107° F.), or the liquid flow is interrupted, thesystem may disable the heaters.

Since the system heats the tube as needed at less than full power andintermittently (e.g., the safety controller disables the heaters inresponse to liquid temperature), the desired set point (i.e.,temperature) is attained rapidly, while the liquid temperature dropsrapidly at shut down (e.g., approximately 13° F. or more in a minutewith reset occurring within one second). The safety controller mayinclude an audible alarm for high and low temperatures that typicallysounds prior to a patient feeling a temperature change. Further, analarm may warn when a liquid-filled bag is at a low level. A change indrip size and/or density may affect the waveshape of the infrareddetectors, thereby activating heaters less within a cycle, while thetemperature decreases. The safety controller can sense this occurrenceand provide an alarm giving advanced warning. Alternatively, two alarmsmay be utilized wherein a first alarm sounds in advance (e.g., duringdepletion of the liquid-filled bag) and a second alarm sounds whenliquid is substantially spent from the liquid-filled bag. The phase downprevents heat residual within the tube.

Tool 88 for inserting a portion of tube 72 within slot 94 of sleeve 92is illustrated in FIGS. 14 and 16. Specifically, tool 88 includes ahandle 89 and tube interface 91. Handle 89 is disposed at the toolproximal end and is generally rectangular having a rounded distal endtoward tube interface 91. Tube interface 91 is disposed at the handledistal end and includes legs 93, 95 each having a curved portion to forma generally semi-circular opening between the legs for receiving tube72. However, the opening may be of any shape or size capable ofreceiving the tube. Legs 93, 95 each transversely extend in opposingdirections from the distal end of their respective curved portion toengage slot 94 and facilitate placement of the tube portion within theheating assembly. The tool receives tube 72 in the opening between legs93, 95, while the transverse portions of the legs penetrate slot 94 toplace the tube portion snugly within the slot adjacent heaters 124 inorder to enable the heaters to heat liquid within the tube. The tool maybe constructed of aluminum or any other suitable materials and may be ofany size or shape, however, by way of example only, the tool includes aheight of approximately three inches.

Drip detector 60 utilizes infrared emitters and detectors, typicallymanufactured by Honeywell, to sense the presence of a drip within thedrip chamber as illustrated in FIGS. 17-18. Specifically, drip detector60 (FIG. 11) includes a substantially rectangular housing having anopening defined through the approximate center of the housing to enabledrip chamber 58 to be disposed through the opening. However, the housingmay be of any shape or size and may be constructed of any suitablematerials. The housing includes a pair of substantially symmetricalhousing blocks 61, 63 housing an infrared emitter and infrareddetectors, respectively. Housing block 61 is substantially rectangularhaving a truncated or cut-off upper side corner (e.g., left side uppercorner as viewed in FIG. 17) and a substantially semi-circular recess 55extending from an upper block edge toward the approximate center of theblock. An infrared emitter 67 is disposed toward the apex of the recessfor emitting infrared energy through the drip chamber. Block 63 issubstantially similar to block 61 and includes a truncated or cut-offlower side corner (e.g., left side lower corner as viewed in FIG. 18)and a substantially semi-circular recess 69 extending from a lower blockedge toward the approximate center of the block. A plurality of infrareddetectors 71, preferably three, are positioned toward the recess apex todetect infrared energy emitted from emitter 67. The detectors detect theinfrared energy emitted from emitter 67, while substantially rejectingambient light. Blocks 61, 63 are connected to form the drip detectorhousing such that the drip chamber is disposed through the generallycircular opening formed by block recesses 55, 69 to enable the emitterand detectors to sense drips within the drip chamber.

Emitter 67 emits a broad signal, typically a 50° conical emission,wherein a drip within the drip chamber focuses the signal on any ofinfrared detectors 71, each generally having a 50° conical window. Theinfrared detector windows overlap each other to provide a wide drip viewand higher count accuracy. The detectors are connected in parallel toeach other within system control circuitry (FIG. 20) to allow morecurrent to flow in the detectors, however, this arrangement slightlydegrades detector current to opticouplers associated with drip countingcircuitry described below. The reduction in current is alleviated byreducing resistance within the circuit. The detectors typically includea high resistance such that when a drip focuses infrared energy on thedetectors, the detectors pass a greater amount of current/voltage to theopticouplers. The passage of varying amounts of current and voltage forma sinusoid wave that the drip counting circuitry may detect and count aspulses. Detectors 71 typically generate analog wave pulses that arecounted by the drip counting circuitry during a specified time interval.One pulse typically includes three-hundred sixty degrees of the analogwave. A continuous or free-flow (e.g., no drips, but rather, acontinuous stream) of liquid virtually always focuses infrared energyonto a detector, thereby enabling the detectors to pass a relativelyhigh constant amount of current/voltage to the opticouplers. Similarly,an interruption in liquid flow enables the detectors to pass arelatively low constant amount of current/voltage to the opticouplerssince the infrared energy is not focused on any detector. Since acontinuous or free-flow of liquid and an interruption in liquid floweach pass a relatively constant amount of current/voltage to theopticouplers, the drip counting circuitry does not detect pulses andtypically produces a zero count in response to these occurrences.

Alternatively, the detectors may generate a high output and transitionto a low output when infrared energy is not detected (i.e., when dripspass through the infrared emission pattern). A high to low transitionwithin the detector output indicates the presence of a drip since thedrip prevents the detectors from sensing the infrared energy. Acontinuous or free-flow of liquid enables the detectors to generate arelatively constant high output, while an interruption in liquid flowenables the detectors to generate a relatively constant low output.Since a continuous or free-flow of liquid and an interruption in liquidflow do not produce any transitions, a zero count is typically producedin response to these occurrences. It is to be understood that thedetectors may be implemented to generate low to high transitions inresponse to detecting a drip wherein the detectors sense drips insubstantially the same manner described above. Since the size of a dripvaries with tubing size and typically changes shape between the top andbottom of a drip tube (e.g., forming the drip chamber), the detectorsare typically positioned such that their overlapping windows cover allareas of the drip tube to ensure that a drip is not missed. Thus, a dripis detected even if the drip tube is slanted and the drip does not passthrough the center of the drip chamber. The detectors are generallyspaced by approximately 24.4°, however, the detectors may be spaced byany amount (e.g., 37°) based on the area needed to be covered and theangle of the conical window. Generally, the angular spacing of detectors71 may be varied by approximately five degrees (e.g., plus or minus fivedegrees) for the arrangement described above. Any quantity of emittersand detectors having dispersion and detection patterns of various angleswith the emitters having the same or different angles as the detectorsmay be utilized, depending upon the strength of signals and areascovered. The emitters and detectors may be positioned in any fashion andmay be implemented by any conventional or other types of emitters anddetectors that accommodate various forms of energy (e.g., light,specific signal frequencies, etc.)

Referring to FIG. 19, thermocouple holder 68 includes a substantiallyflat rectangular base or platform 73, having curved prongs 75, 77extending down from the platform and curving toward each other. Prongs75, 77 each include transversely extending projections 85, 87 thatextend from their respective prongs toward each other. A channel 79 isdisposed below platform 73 to receive tube 72 (FIG. 11), whiletemperature sensor 86 (FIGS. 13-15) is disposed between projections 85,87 of prongs 75, 77 proximate tube 72 to obtain an accurate temperaturemeasurement of the liquid in the tube. The thermocouple holder istypically attached to a patient with platform 73 interfacing a patientbody part, such as an arm. The thermocouple holder ensures propermounting of temperature sensor 86 and enables accurate temperaturecontrol via a precise temperature measurement of liquid within tube 72(i.e., not skin or ambient temperature) wherein the temperature sensorprovides a true liquid temperature measurement. The temperature sensoris typically matched to the safety controller described above to provideaccuracy and increased sensitivity and precision. A safety circuit 81 isdisposed adjacent channel 79 between platform 73 and prong 77. Thesafety circuit must be complete or closed to enable operation of thesystem. The heat controller described above monitors the circuit anddisables operation when the circuit is broken or open. The safetycircuit may include a resistor across wires that creates a specificresistance detected by the heat controller. Alternatively, the safetycircuit may be implemented by a Hall effect transistor that switchesbased on magnetic fields. Magnetic beads may be disposed within thethermocouple holder wherein the beads are matched to the transistor(e.g., as to strength of the field). The transistor senses the beads toenable system operation. Thermocouple holder 68 and tube 72, typicallywith Luer locks (e.g., male and female), are generally disposablewherein thermocouple holder 68 is typically attached (e.g., via anapproved medical biocompatible adhesive) to a patient near the entrysite for infused liquids. The thermocouple holder may be implementedwith a butterfly base, may be attached to a patient in any fashion atany location, may be of any size or shape and may be constructed ofplastic or any other suitable materials, however, by way of exampleonly, the holder has a height slightly less than approximately one inchand a width (e.g., between prongs) of slightly less than approximatelyone-half inch.

A circuit for controlling system operation is illustrated in FIG. 20.Specifically, the control circuit includes lines 102, 104 and 106extending from a common wall outlet jack receptacle 108. A fuse 110 isconnected in series with line 102 from receptacle 108 between thereceptacle and a power switch 112. Power switch 112 enables power to thecircuit from lines 102, 104 (e.g., line voltage (e.g., 120V AC) istypically provided to a power supply 116, the load side of solid staterelays 122 and a safety controller 114 each described below). Powersupply 116, typically 120V AC having +/−12V DC, +/−5V DC, +5V and −5V DCoutputs (e.g., fused at the power supply and generally on the device(e.g., control circuit and/or circuit board 118)), is connected to powerswitch 112 and provides power to safety controller 114, a circuit board118, and heaters 124. All control and processor functions are performedat low voltage. Safety controller 114, typically implemented by a Loveor Eurotherm controller, receives power from power supply 116 and atemperature signal from temperature sensor 86 (e.g., an RTD sensor istypically utilized with a Love controller, while an infrared sensor istypically utilized with a Eurotherm controller) indicating thetemperature of the liquid. Safety controller 114 may alternatively beimplemented by any conventional or other processor, controller orcircuitry. The true temperature is received by safety controller 114from the infrared sensor such that no additional calculations arerequired. The safety controller, typically implemented as a safetyoverride, respectively displays the liquid and set point temperatures ondisplays 74, 76 (FIG. 12), and is connected in series to a plurality ofsolid state heat relays 122 that control power to heaters 124, or analarm relay (not shown). Each solid state relay is further connected toan indicator light 84 of control panel box 70 to indicate the status(i.e., on/off) of a corresponding heater. When the temperature signalfrom temperature sensor 86 indicates that the liquid temperature equalsor exceeds a predetermined or desired liquid temperature, safetycontroller 114 disables power (e.g., cuts line voltage or opens relays122) to heaters 124. If temperature sensor 86 fails, safety controller114 defaults to open circuit (e.g., opens relays 122 to disable heaters124) and the display flashes alarm. The Eurotherm controller includes asensor brake alarm loop, temperature response alarm loop and a hightemperature alarm, while the Love controller includes a high temperaturealarm and sensor brake alarm loop.

Circuit board 118 houses the circuitry that maintains a drip count andcontrols heaters 124 in response to liquid flow rate. The circuit boardincludes a heat controller or processor 120 that, via software,manipulates solid state relays 122 to control individual heaters 124 inresponse to drip counts. The processor, preferably a Parallax BS2 (i.e.,Basic Stamp configuration), typically utilizes binary, hexadecimal andBasic programming and includes defaults of no outputs and inputs on(e.g., the processor defaults to having no outputs). Each softwareinstruction is typically executed within one microsecond and theprocessor includes 5V, 25 ma (i.e., milliamp) outputs for control of thetemperature control system. The circuit board further receives signalsfrom safety circuit 81 to disable the system when a complete circuit isnot detected, and displays the drip count for a predetermined timeinterval on display 82. Infrared emitter 67 and detectors 71 areconnected to the circuit board wherein detectors 71 transmit signalsindicating the presence of a drip as described above to enable thecircuit board to count drips. Any quantity of detectors detecting a dripmay enable incrementation of the drip count, however, by way of exampleonly, drip detection by any of the detectors increments the drip count.The drip count is sent to processor 120 to manipulate individual heatersas described above.

Referring to FIG. 21, circuit board 118 includes processor 120,opticoupler circuit 128 for infrared emitter and detectors, a countingcircuit 126 and display 82. The processor and opticoupler areimplemented by conventional integrated circuits, while the countingcircuit preferably includes two conventional integrated circuits. Theprocessor, opticoupler and counting circuits may be implemented by anyconventional or other circuitry capable of receiving signals fromdetectors 71 and producing a drip count. Counting circuit 126 incrementsa count for each drip detected within the drip chamber, and may be resetby processor 120. Infrared detectors 71 are coupled to the countingcircuit via opticoupler circuit 128 such that the counting circuitincrements the count for each drip detected by the detectors. Theopticoupler circuit essentially receives signals from detectors 71 anddetermines from those signals whether or not a drip is present. Theopticoupler subsequently sends a signal to counting circuit 126 toincrement the count in response to detection of a drip wherein the countis displayed on display 82. Processor 120 receives the drip count and,in combination with safety controller 114 (FIG. 20), controls heaters124, via software, to maintain liquid within tube 72 (FIG. 11) at adesired temperature.

A procedural flow chart for safety controller 114 to display measuredliquid and set point temperatures and control heaters 124 in response toliquid temperature is illustrated in FIG. 22. Specifically, safetycontroller 114 (FIG. 20) is enabled and displays the liquid temperaturedetected by temperature sensor 86 and the set point temperature (i.e.,predetermined or desired liquid temperature) entered via buttons 78(FIG. 12) on displays 74, 76, respectively. The sensed temperature iscompared to the set point temperature by the safety controller todetermine if the sensed temperature is below the set point temperature.The safety controller sounds an alarm when the sensed temperatureexceeds the set point temperature by at least two degrees (e.g.,Fahrenheit or Celsius depending upon the scale utilized), whiledisabling power to heaters 124 (e.g., cutting line voltage or openingsolid state relays 122) in response to the sensed temperature beingequal to or exceeding the set point temperature by any margin. However,the safety controller may be programmed to sound the alarm when thesensed temperature exceeds the set point temperature by any desiredamount. If the sensed temperature is below the set point temperature,the safety controller maintains power to heaters 124 (e.g., maintainsline voltage or closes solid state relays 122) to enable heat controlleror processor 120 to control temperature of the liquid based on measureddrip counts as described below. Safety controller 114 repeatedlycompares sensed liquid temperatures to the set point temperature tocontrol heaters 124 as described above until processing is complete(e.g., power down of the system). Disablement of heaters 124 by thesafety controller overrides any controls issued by the heat controller,however, the heat controller continues to generate heater controls asdescribed below whether or not the heater controls are overridden by thesafety controller.

A procedural flowchart for heat controller or processor 120 (FIG. 20) tocontrol heaters 124 based on liquid flow rate is illustrated in FIG. 23.The processor software is implemented such that only one command or stepmay be performed at any one time in sequential order. Generally,processor 120 requests the drip counting circuitry (e.g., the infrareddetectors, opticoupler circuit and counting circuit (FIG. 21)) togenerate drip counts for predetermined time intervals wherein theprocessor utilizes the drip counts to control heaters 124. Processor 120further monitors liquid flow and disables heaters 124 in response todetecting a free-flow of liquid or an interruption of liquid flow toprevent residual heat from reaching a patient. In addition, processor120 disables system operation in response to safety circuit 81 beingopen during liquid flow (e.g., the safety circuit is open when afree-flow of liquid or an interruption of liquid flow has each notoccurred). Specifically, power is enabled to processor 120 at step 150and the processor resets the system at step 152 by initializingvariables and system parameters to particular values (e.g., zero). Theprocessor requests that a drip count be generated by the drip countingcircuitry for a predetermined time interval at step 154 wherein the dripcount result is stored in memory, while changes in the drip count arealso stored in memory during software execution. The drip count isinspected by the processor at step 156 to determine whether or not afree-flow of liquid or an interruption of liquid flow has occurred(e.g., a drip count of zero for a predetermined time interval indicatesa free-flow of liquid or an interruption of liquid flow as describedabove). If a free-flow of liquid or an interruption of liquid flow hasoccurred (e.g., the drip count for a predetermined time interval equalszero), processor 120, at step 158, disables heaters 124 and sounds analarm until the processor determines at step 160 that the liquid flowsat a drip flow rate (e.g., until the drip detector senses drips withinthe drip chamber or, in other words, the drip count for a predeterminedtime interval is greater than zero).

When the processor determines at step 160 that the liquid flows at adrip flow rate, the processor inspects safety circuit 81 at step 162.This is typically accomplished by examining a circuit variable storedwithin the processor memory and having a value generated from a poll ofthe safety circuit wherein the circuit variable value corresponds to thesafety circuit status. By way of example only, a circuit variable valueequal to or greater than one indicates proper operation or a completesafety circuit, however, the circuit variable may have any values toindicate the safety circuit status. If processor 120 determines thatsafety circuit 81 is complete at step 162 (e.g., the circuit variablehas a value equal to or greater than one), the processor disablesheaters 124 and sounds an alarm at step 192, and subsequently resets thesystem for a new cycle at step 152. Otherwise, in response todetermining that the safety circuit is open at step 162 (e.g., thecircuit variable has a value less than one), processor 120 inspects thedrip count at step 188 to detect a free-flow of liquid or aninterruption in liquid flow. When a free-flow of liquid and aninterruption of liquid flow has each not occurred (e.g., the drip countfor a predetermined time interval is greater than zero), processor 120disables heaters 124 and sounds an alarm at step 190, and subsequentlyterminates system operation. However, in response to detecting afree-flow of liquid or an interruption of liquid flow at step 188 (e.g.,the drip count for a predetermined time interval equals zero), processor120 disables heaters 124 and sounds an alarm at step 192, andsubsequently resets the system for a new cycle at step 152.

In response to determining at step 156 that a free-flow of liquid and aninterruption of liquid flow has each not occurred (e.g., the drip countfor a predetermined time interval is greater than zero), processor 120utilizes the drip count to determine, at step 164, an appropriatecontrol scheme for heaters 124 (e.g., the specific heaters to activateand the length of time of their activation). Specifically, the dripcount is compared to values within a series of logical expressionsformed in a priority hierarchy with instructions (e.g., heater controlschemes) associated with higher priority expressions executed first. Theinstructions associated with a first true logical expression areexecuted even if other lower expressions are true. If the drip countdoes not correspond with a heater control scheme (e.g., the drip countdoes not correspond to a particular count or range associated with acontrol scheme), processor 120 disables heaters 124 and sounds an alarmat step 192, and subsequently resets the system for a new cycle at step152. When a drip count corresponds to a heater control scheme (e.g., thedrip count corresponds to a particular count or range associated with acontrol scheme), that heater control scheme is executed at step 166.

Processor 120, at initial execution of a control scheme, inspects safetycircuit 81 at step 168. If processor 120 determines at step 168 thatsafety circuit 81 is not complete (e.g., the circuit variable has avalue less than one), the processor inspects the drip count at step 188to detect a free-flow of liquid or an interruption of liquid flow. Whena free-flow of liquid and an interruption of liquid flow has each notoccurred (e.g., the drip count for a predetermined time interval isgreater than zero), processor 120 disables heaters 124 and sounds analarm at step 190, and subsequently terminates system operation.However, in response to detecting a free-flow of liquid or aninterruption of liquid flow at step 188 (e.g., the drip count for apredetermined time interval equals zero), processor 120 disables heaters124 and sounds an alarm at step 192, and subsequently resets the systemfor a new cycle at step 152. When processor 120 determines at step 168that safety circuit 81 is complete (e.g., the circuit variable has avalue equal to or greater than one), the processor determines at step170 whether or not a free-flow of liquid or an interruption of liquidflow has occurred. If a free-flow of liquid or an interruption of liquidflow has occurred (e.g., the drip count for a predetermined timeinterval equals zero), processor 120 disables heaters 124 and sounds analarm at step 192, and subsequently resets the system for a new cycle atstep 152.

When processor 120 respectively determines at steps 168 and 170 thatsafety circuit 81 is complete (e.g., the circuit variable has a valueequal to or greater than one) and a free-flow of liquid and aninterruption of liquid flow has each not occurred (e.g., the drip countfor a predetermined time interval is greater than zero), processor 120performs the control scheme associated with the drip count at step 172wherein specific heaters 124 are activated for a particular timeinterval, while the appropriate heater indicator lights are illuminated.During a heating cycle, processor 120, at step 174, conducts aninspection approximately every ten seconds or any other time interval toensure that safety circuit 81 remains complete and that the liquid flowhas not been changed (e.g., user intervention to enable free-flow ofliquid or an interruption of liquid flow). If processor 120 determinesat step 176 that liquid flow has been altered (e.g., the drip count fora predetermined time interval equals zero indicating a free-flow ofliquid or an interruption of liquid flow), processor 120, at step 178,disables heaters 124 and sounds an alarm until the processor determinesat step 180 that the liquid flows at a drip flow rate (e.g., the dripcount for a predetermined time interval is greater than zero) asdescribed above.

When processor 120 determines at step 180 that the liquid flows at adrip flow rate, the processor inspects safety circuit 81 at step 182. Ifprocessor 120 determines that safety circuit 81 is complete at step 182(e.g., the circuit variable has a value equal to or greater than one),the processor disables heaters 124 and sounds an alarm at step 192, andsubsequently resets the system for a new cycle at step 152. Otherwise,in response to determining that safety circuit 81 is open at step 182(e.g., the circuit variable has a value less than one), processor 120inspects the drip count at step 188 to detect a free-flow of liquid oran interruption in liquid flow. When a free-flow of liquid and aninterruption of liquid flow has each not occurred (e.g., the drip countfor a predetermined time interval is greater than zero), processor 120disables heaters 124 and sounds an alarm at step 190, and subsequentlyterminates system operation. However, in response to detecting afree-flow of liquid or an interruption of liquid flow at step 188 (e.g.,the drip count for a predetermined time interval equals zero), processor120 disables heaters 124 and sounds an alarm at step 192, andsubsequently resets the system for a new cycle at step 152.

Referring back to step 176, when a free-flow of liquid and aninterruption of liquid flow has each not occurred (e.g., the drip countfor a predetermined time interval is greater than zero), processor 120inspects safety circuit 81 at step 184. If processor 120 determines atstep 184 that safety circuit 81 is not complete (e.g., the circuitvariable has a value less than one), the processor inspects the dripcount at step 188 to detect a free-flow of liquid or an interruption ofliquid flow. When a free-flow of liquid and an interruption of liquidflow has each not occurred (e.g., the drip count for a predeterminedtime interval is greater than zero), processor 120 disables heaters 124and sounds an alarm at step 190, and subsequently terminates systemoperation. However, in response to detecting a free-flow of liquid or aninterruption of liquid flow at step 188 (e.g., the drip count for apredetermined time interval equals zero), processor 120 disables heaters124 and sounds an alarm at step 192, and subsequently resets the systemfor a new cycle at step 152.

When processor 120 respectively determines at steps 176 and 184 that afree-flow of liquid and an interruption of liquid flow has each notoccurred (e.g., the drip count for a predetermined time interval isgreater than zero) and that safety circuit 81 is complete (e.g., thecircuit variable has a value equal to or greater than one), theprocessor determines at step 186 whether or not a control scheme orcycle is complete. In response to completion of a cycle, processor 120resets the system for a new cycle at step 152; otherwise, the processorcontinues inspecting liquid flow and the safety circuit at predeterminedtime intervals as described above (i.e., steps 174, 176, and 184) untilthe cycle is complete. Heaters 124 are controlled by processor 120 inthe manner described above wherein the heaters function in accordancewith controls received from processor 120 unless safety controller 114disables the heaters as described above. However, processor 120continues to generate controls for heaters 124 as described abovewhether or not the controls from the processor have been overridden bythe safety controller. In other words, processor 120 continues togenerate heater controls even if the heaters are prevented fromfunctioning in response to those controls.

The temperature control system may further include multiple chips (e.g.,controllers) to permit greater simultaneous functionality (e.g.,temperature control of multiple bags having different uses, such asintravenous and irrigation). Further, the temperature control system maybe controlled via a personal or other type of computer from a remotelocation, such as a lab. The remote system may control temperature andflow rate wherein troubleshooting may further be accomplished via modemfrom a remote location.

Alternatively, heating assembly 64 may contain a single heater and beused in combination with a heated liquid-filled bag as illustrated inFIG. 24. Specifically, the configuration illustrated in FIG. 24 issimilar to the configuration illustrated in FIG. 11 and includesreceptacle 6, drip chamber 58, tube 72, roller lock 62 and connector 66,each as described above for FIG. 11. The configuration further includescontrol box 40, as described above for FIG. 11, housing a heater controlcircuit (FIG. 25) and a heating assembly 64 that is substantiallysimilar to the heating assembly described above for FIGS. 13-15 exceptthat a single elongated heater or heating element 132 is utilized withinheating assembly sleeve 92. Heater 132 is similar to heating element 36(FIG. 9) described above, and is controlled by a controller based onsensed resistance in heater 132 in substantially the same mannerdescribed above for the heated pressurized infusion system. Receptacle 6typically contains liquid-filled bag 14, conductive plate 38 (FIG. 8)and heating element 36 (FIG. 9) as described above for the heatedpressurized infusion system. The heating element and conductive platemay be disposed on a bellows bag 32 (FIG. 5), containing a bellows andpositioned adjacent the liquid-filled bag within receptacle 6, to heatthe liquid-filled bag as described above. However, the heating elementand conductive plate may be utilized without the bellows and bellows bagand may be disposed within the receptacle in any fashion. Drip chamber58 is coupled to liquid-filled bag 14 wherein tube 72 extends from thedrip chamber and traverses roller lock 62, heating assembly 64 andconnector 66 as described above for FIG. 11 to direct heated liquid fromthe liquid-filled bag to an entry site on a patient. A portion of tube72 is disposed within heating assembly sleeve 92 as described above toenable heating assembly 64 to maintain the heated liquid at a desiredtemperature and prevent liquid cooling as the heated liquid flows withinthe tube from liquid-filled bag 14 to a patient.

A control circuit for controlling heating element 36 and heater 132 isillustrated in FIG. 25. The control circuit is substantially similar tothe circuit described above for FIG. 10 except that the control circuitincludes an additional controller 130 to control heater 132 of heatingassembly 64. Controller 130 is substantially similar to controller 56and controls power to heater 132. Specifically, power switch 52 enablespower to power supply 54 as described above wherein the power supplydirects power to controllers 56, 130 and corresponding heating element36 and heater 132, respectively. Controller 56 senses resistance withinheating element 36 and controls power to the heating element to maintainthe heating element and liquid-filled bag at a desired temperature asdescribed above. Controller 130 senses resistance within heater 132 andcontrols power to that heater in substantially the same manner describedabove for controller 56 to maintain the heater and heated liquid withintube 72 at a desired temperature as the heated liquid flows within thetube from the liquid-filled bag to a patient.

It will be appreciated that the embodiments described above andillustrated in the drawings represent only a few of the many ways ofimplementing a method and apparatus for pressure infusion andtemperature control of infused liquids.

The various embodiments of the present invention, namely the pressurizedinfusion systems and the temperature control systems may be utilizedeither individually or in any combination to warm liquid. For example,the non-heated pressurized infusion system may be utilized individuallyor in combination with the multiple heater temperature control system,while the heated pressure infusion system may be utilized individuallyor in combination with the single heater temperature control system.Further, the systems may be utilized for any applications requiringheated fluids, or fluids heated during fluid flow.

The receptacle may be of any shape or size, and may be constructed ofany suitable materials. Further, the receptacle may be attached tointravenous poles or other structures via any type of hook, opening orby any other fastening techniques. The receptacle may include any typeof zipper or other fastening devices disposed anywhere on the receptaclein any fashion to close the compartment. The pressure gauge may beimplemented by any conventional or other type of device for measuringand indicating pressure levels, and may be disposed on the receptacle,intravenous pole or at any other location capable of conveying pressurereadings to a user.

The bellows may be implemented by any inflatable device capable ofexpanding upon inflation, and may be inflated via any type of fluid,such as a gas (e.g., air) or liquid. The bellows may be of any shape orsize capable of applying pressure to the liquid-filled bag, may beconstructed of any suitable materials, and may be oriented in anyfashion within the bellows bag or receptacle. Further, any quantity(e.g., at least one) of bellows may be utilized to apply pressure to theliquid-filled bag in substantially the same manner described above. Thebellows port may be disposed anywhere on the bellows. The bellows may beutilized without being disposed within the bellows bag. The bellows bagmay be of any shape or size capable of receiving the bellows or coveringany portion of the bellows, and may be constructed of any suitablematerials. The bellows bag opening may be of any shape or size and maybe disposed anywhere on the bellows bag capable of enabling insertion ofthe bellows into the bellows bag. The bellows bag opening may be coveredby any flap or other object to maintain the bellows within the bellowsbag. The port opening in the bellows bag may be of any shape or size andmay be disposed at any location capable of enabling fluid transferbetween the bellows and an inflation/deflation device. The hose fordirecting fluid to and from the bellows may be implemented by anyconventional or other type of hose or tube, may be of any size or shape,and may be constructed of any suitable materials. The bellows bagopening may alternatively be utilized for receiving hoses or tubes forfacilitating fluid transfer between the bellows and aninflation/deflation device. The bellows bag pocket may be of any shapeor size, and may be disposed anywhere on the bag to enable the heatingelement and conductive plate to be applied to the liquid-filled bag. Thebellows may be inflated by any type of inflating device or pumpincluding any type of valve or other device for controlling inflationand deflation of the bellows.

The heating element and conductive plate may be of any shape or size,and may be constructed of any materials capable of conducting heat. Theheating element may be utilized without the conductive plate, may bedisposed adjacent the liquid-filled bag, and may be implemented by anytype of heater or heating element. The heating element and conductiveplate may alternatively be disposed anywhere proximate the liquid-filledbag to heat that bag, and not necessarily within the receptacle. Thepressurized and heated pressurized infusion systems are not limited toapplication with intravenous poles, but may be utilized with variousstructures.

The heating element temperature may be measured by any conventional orother type of temperature measuring devices to control heating elementtemperature. The heating element control circuitry may include anyconventional or other type of power switch (e.g., lighted), power supplyand controller. The heating element controller is typically implementedby a commercially available controller pre-programmed and loaded withits own software, but may be implemented by any conventional or othertype of controller, microprocessor, or circuitry capable of controllingthe heating element to attain a desired temperature. The control box maybe of any shape or size, and may be constructed of any suitablematerials. The control box may be disposed on an intravenous pole or atany location capable of enabling the heating element control circuit tocontrol the heating element.

The control panel box may be of any shape or size, and may disposedanywhere on an intravenous pole or at any other location capable ofcontrolling the heating assembly. The control panel front surface mayinclude any types of displays, lights or other indicators, or switches(e.g., lighted) arranged in any fashion. The displays may be implementedby any conventional or other types of displays, such as LED or LCDdisplays. The indicator lights may be implemented by any type of lightor other indicator, such as audio, voice or display, to indicate heateractivation. The power switch may be implemented by any type ofconventional or other type of switch or button that may include a lightfor illuminating the switch or button. The displays may display anyquantity of digits to reflect the actual and set point temperatures.

The heating assembly sleeve may be of any shape or size, and may beconstructed of any suitable materials. The slot may be of any length andbe defined anywhere in the sleeve to engage the tube. Alternatively, thesleeve may include any type of fastener to engage the tube. The sleevemay include channels or other openings disposed anywhere on the sleeveto accommodate wiring. The heaters may be disposed anywhere within oradjacent the sleeve capable of heating the tube. The sleeve may includeany quantity of heaters (e.g., at least one) to heat the tube. Thesleeve may be encased by a jacket of any shape or size and constructedof any suitable materials. The jacket may include any type of zipper orother fastener to maintain the sleeve within the jacket. The temperaturesensor may be implemented by any conventional or other type of infrared,resistive temperature (RTD) or other temperature sensing devices. Theheating assembly may be disposed anywhere along the tube and accommodateany sized portion of the tube to heat the liquid, while the tube may beimplemented by any conventional intravenous or other type of tube. Thedrip chamber may be implemented by any conventional drip chamber orother device that enables the fluid to drip. The drip detector mayinclude any type of mechanical or other type of detector to detectdrips. The emitter may be implemented by any conventional infrared orother type of emitter to detect the drip, such as emitters fortransmitting signals at infrared or any other frequency or light band.The detectors may be implemented by any conventional infrared or othertype of detector capable of detecting the signal emitted by the emitter.The drip detector may include any quantity of emitters and detectors(e.g., at least one emitter and one detector). The drip detector housingmay be of any shape, and may be constructed of any suitable materials.The drip detector may be disposed at any location near the drip chambercapable of detecting a drip. The emitter may have any type of emissionspread (e.g., conical) with any angle, while each detector may includeany detection window (e.g., having any angle) to detect the emittersignal. The emitter and detectors may be arranged in any fashion withinthe drip detector housing to detect a drip.

The control circuitry for the temperature control system may include anyconventional or other types of fuses, receptacles, controllers, switches(e.g., lighted), power supplies, and relays. The safety controller istypically implemented by a commercially available pre-programmedcontroller loaded with its own software, but may be implemented by anytype of controller, microprocessor or other circuitry capable ofdisabling the heaters in response to a temperature measurement. Thepower supply may be implemented by any conventional or other type ofpower supply, while the solid state relays may be implemented by anytype of solid state or other relays or switches. The power switch may beimplemented by any conventional or other type of switch (e.g., lighted)or button. The heat controller may be implemented by any type ofcontroller, microprocessor or other circuitry capable of controlling theheaters in response to flow rate. The heat controller or processor andsafety and heating element controllers, if the safety and heatingelement controllers are implemented by a programmable controllerrequiring software, may be programmed in any suitable computer languagewherein the program and algorithm may be modified in any fashion tocontrol heaters for maintaining liquid temperature. For example, thetime intervals for maintaining heater activation may be adjusted tocontrol heating of the liquid within the tube based on a desired drip orflow rate. It is to be understood that one of ordinary skill in thecomputer and/or programming arts can develop the software for the heatcontroller or processor and heating element and safety controllers, ifthe heating element and safety controllers are implemented byprogrammable controllers requiring software, based on the functionaldescription of controller operation in the specification and flow chartsillustrated in the drawings.

The circuit board may include any type of circuitry to interpretdetector signals and increment a counter. The counter may be implementedby any conventional or other type of counting circuitry, such asintegrated circuits, a microprocessor, registers, memory, etc. Theopticouplers may be implemented by any conventional or other type ofopticoupler or other circuitry capable of receiving detector signals anddetermining whether or not to increment a counter.

The thermocouple holder may be of any size or shape, and may beconstructed of any suitable materials. The thermocouple holder mayreceive the tube and sensor in any fashion to enable the sensor toobtain temperature measurement of the liquid within the tube. The holdermay be disposed at any location near the entry site, and may be attachedto a patient via any suitable fastening technique. The safety circuitmay be implemented by any type of circuit enabling operation of thesystem wherein any values may be utilized within the heat controller toindicate safety circuit status (e.g., complete or open).

The single heater temperature control system may include any type ofheating element or heater disposed within the heating assembly. Theheating element may be of any size or shape, and may be disposed at anylocation within the sleeve capable of heating the liquid within thetube. The control circuit of the single heater temperature controlsystem may include any conventional or other type of fuse, power switch(e.g., lighted) or controllers as described above for the controlcircuit of the heated pressurized infusion system. The controllers ofthe single heater temperature control system may be implemented by anycontrollers, microprocessors or other circuitry capable of controllingthe heating element and heater in response to a temperature measurementas described above.

It is to be understood that the heating assembly heaters may becontrolled by the heat controller based on the relationship between flowrate, liquid viscosity and temperature. The relationship between theviscosity and temperature of any liquid is known. Since the viscosity ofthe infused liquid is known, and the flow rate is measured, thetemperature of the liquid, and hence, heater operation may be controlledbased on the known viscosity and measured flow rate. That is, the heatcontroller may control the heating assembly heaters based on flow rate(e.g., and known viscosity) to maintain liquid temperature atsubstantially a desired temperature. From the foregoing description, itwill be appreciated that the invention makes available a novel methodand apparatus for pressure infusion and temperature control of infusedliquids wherein an inflatable device is disposed adjacent aliquid-filled bag to apply pressure to the liquid-filled bag to driveliquid from the liquid-filled bag to a patient, while the inflatabledevice may further include a conductive plate and heating element toapply heat to the liquid-filled bag. Further, a heating assemblyincluding at least one heater may be disposed along an intravenous orother tube to heat liquid flowing within the tube from a liquid-filledbag to a patient.

Having described preferred embodiments of a new and improved method andapparatus for pressure infusion and temperature control of infusedliquids, it is believed that other modifications, variations and changeswill be suggested to those skilled in the art in view of the teachingsset forth herein. It is therefore to be understood that all suchvariations, modifications and changes are believed to fall within thescope of the present invention as defined by the appended claims.

1-40. (canceled)
 41. In an apparatus for controlling temperature of infused liquids as liquid flows from a liquid-filled container through a drip chamber and tube to an entry site on a patient, wherein said drip chamber includes a transparent tube and is disposed along said tube subsequent said liquid-filled container, an apparatus for detecting drips within said drip chamber comprising: a housing including an opening for receiving said drip chamber; at least one emitter disposed within said housing for emitting signals through said transparent tube in the form of non-visible light to minimize the effect of ambient visible light in the vicinity of said transparent tube; and a plurality of detectors disposed within said housing for detecting said non-visible light signals emitted by said at least one emitter and modified by drips within said transparent tube to sense the presence of drips within said drip chamber.
 42. The apparatus of claim 41 wherein said housing includes an exterior surface disposed along a periphery of said opening, and said detectors are disposed within said housing at said exterior surface.
 43. The apparatus of claim 41 wherein said detectors are positioned within said housing to receive said ambient visible light through said transparent tube without permitting said received ambient visible light to affect said drip detection.
 44. The apparatus of claim 42 wherein said apparatus includes one emitter, and said one emitter is disposed at said exterior surface of said housing.
 45. In an apparatus for controlling temperature of infused liquids as liquid flows from a liquid-filled container through a drip chamber and tube to an entry site on a patient, wherein said drip chamber includes a transparent tube and is disposed along said tube subsequent said liquid-filled container, and said apparatus includes a drip detector having a housing including an opening, a method for detecting drips within said drip chamber comprising the steps of: (a) disposing said drip chamber through said opening of said housing; (b) emitting signals through said transparent tube in the form of non-visible light, via at least one emitter disposed within said housing, to minimize the effect of ambient visible light in the vicinity of said transparent tube; and (c) detecting said non-visible light signals emitted by said at least one emitter and modified by drips within said transparent tube, via a plurality of detectors, to sense the presence of drips within said drip chamber.
 46. The method of claim 45 wherein said housing includes an exterior surface disposed along a periphery of said opening, and step (c) further includes: (c.1) positioning said detectors within said housing at said exterior surface.
 47. The method of claim 45 wherein step (c) further includes: (c.1) positioning said detectors within said housing to receive said ambient visible light through said transparent tube without permitting said received ambient visible light to affect said drip detection.
 48. The method of claim 46 wherein said drip detector includes one emitter, and step (c) further includes: (c.2) disposing said one emitter at said exterior surface of said housing. 